The present invention relates generally to aerosol generators and, more particularly, to aerosol generators able to generate aerosols without compressed gas propellants and methods of making and using such aerosol generators. The present invention also relates generally to metering valves in inhalers and, more particularly, to metering valves which deliver a predetermined volume in inhalers including aerosol generators able to generate aerosols without compressed gas propellants.
Aerosols are useful in a wide variety of applications. For example, it is often desirable to treat respiratory ailments with, or deliver drugs by means of, aerosol sprays of finely divided particles of liquid and/or solid, e.g., powder, medicaments, etc., which are inhaled into a patient's lungs. Aerosols are also used for purposes such as providing desired scents to rooms, applying scents on the skin, and delivering paint and lubricant.
Various techniques are known for generating aerosols. For example, U.S. Pat. Nos. 4,811,731 and 4,627,432 both disclose devices for administering medicaments to patients in which a capsule is pierced by a pin to release a medicament in powder form. A user then inhales the released medicament through an opening in the device. While such devices may be acceptable for use in delivering medicaments in powder form, they are not suited to delivering medicaments in liquid form. The devices are also, of course, not well-suited to delivery of medicaments to persons who might have difficulty in generating a sufficient flow of air through the device to properly inhale the medicaments, such as asthma sufferers. The devices are also not suited for delivery of materials in applications other than medicament delivery.
Another well-known technique for generating an aerosol involves the use of a manually operated pump which draws liquid from a reservoir and forces it through a small nozzle opening to form a fine spray. A disadvantage of such aerosol generators, at least in medicament delivery applications, is the difficulty of properly synchronizing inhalation with pumping. More importantly, however, because such aerosol generators tend to produce particles of large size, their use as inhalers is compromised because large particles tend to not penetrate deep into the lungs.
One of the more popular techniques for generating an aerosol including liquid or powder particles involves the use of a compressed propellant, often containing a chloro-fluoro-carbon (CFC) or methylchloroform, to entrain a material, usually by the Venturi principle. For example, inhalers containing compressed propellants such as compressed gas for entraining a medicament are often operated by depressing a button to release a short charge of the compressed propellant. The propellant entrains the medicament as the propellant flows over a reservoir of the medicament so that the propellant and the medicament can be inhaled by the user. Since the medicament is propelled by the propellant, such propellant-based arrangements are well-suited for those who might have difficulty inhaling. Nonetheless, aerosols generated by propellant-based arrangements have particles that are too large to ensure deep lung penetration.
In propellant-based arrangements, however, a medicament may not be properly delivered to the patient's lungs when it is necessary for the user to time the depression of an actuator such as a button with inhalation. Moreover, such arrangements tend to be poorly suited for delivery of materials in large quantities. Although propellant-based aerosol generators have wide application for uses such as antiperspirant and deodorant sprays and spray paint, their use is often limited because of the well-known adverse environmental effects of CFC's and methylchloroform, which are among the most popular propellants used in aerosol generators of this type.
In drug delivery applications, it is typically desirable to provide an aerosol having average mass median particle diameters of less than 2 microns to facilitate deep lung penetration. Most known aerosol generators are incapable of generating aerosols having average mass median particle diameters less than 2 to 4 microns. It is also desirable, in certain drug delivery applications, to deliver medicaments at high flow rates, e.g., above 1 milligram per second. Most known aerosol generators suited for drug delivery are incapable of delivering such high flow rates in the 0.2 to 2.0 micron size range.
U.S. Pat. No. 5,743,251, which is hereby incorporated by reference in its entirety, discloses an aerosol generator, along with certain principles of operation and materials used in an aerosol generator, as well as a method of producing an aerosol, and an aerosol. The aerosol generator disclosed according to the '251 patent is a significant improvement over earlier aerosol generators, such as those used as inhaler devices. It is desirable to produce an aerosol generator that is portable and easy to use.
According to one aspect of the present invention, an aerosol generator includes a flow passage such as a tube having an inlet and an outlet, a heater arranged relative to the flow passage for heating at least a portion of the flow passage, a source of material to be volatilized, the inlet of the flow passage being in communication with the source of material, and a valve operatively located between the source of material and the flow passage, the valve being openable and closeable to open and close communication between the source and the outlet of the flow passage. A pressurization arrangement is provided for causing material in the source of material to be introduced into the flow passage from the source of material when the valve is in an open position. A source of power is provided for operating the heater and for the valve, and a control device is provided for controlling supply of power from the source of power to the heater and the valve.
According to a further aspect of the present invention, a method of making an aerosol generator is disclosed. According to the method, a heater is arranged relative to a flow passage for heating of the flow passage, the flow passage having an inlet and an outlet. The inlet of the flow passage is connected to a source of material to be volatilized. An openable and closeable valve is provided between the source of material and the flow passage. A pressurization arrangement is provided for causing material in the source of material to be introduced into the flow passage from the source of material when the valve is in an open position. The valve is connected to a source of power for opening and closing the valve. The heater is connected to the source of power. The source of power is connected to a control device for controlling a supply of power from the source of power to the heater and the valve.
According to yet another aspect of the present invention, a method of generating an aerosol is disclosed. According to the method, a first signal indicative of a user's intention to generate an aerosol, is generated and sent to a control device. With the control device and responsive to the first signal, a second signal is sent to a source of power to cause the source of power to open an openable and closeable valve, the valve being disposed between a source of material to be volatilized and a flow passage, opening of the valve permitting material from the source of material to flow from the source of material and into the flow passage. Material from the source of material is thus caused to flow from the source of material and into the flow passage. With the control device and responsive to the first signal, a third signal is sent to the source of power to supply power to a heater disposed relative to the flow passage to heat the flow passage. Material from the source of material is heated in the flow passage with the heater to a vaporization temperature such that the material volatilizes and expands out of an outlet of the flow passage.
The present invention also provides a metering device in an inhaler having a pressurized source of medicated fluid and a metering chamber in fluid communication with the pressurized source of fluid. The metering chamber is configured to deliver a predetermined volume of fluid to a heated flow passage in an inhaler.
In accordance with one embodiment of the metering device, the metering chamber is a rotary valve including a bore and a displacement member located within the bore. The displacement member is movable from a first position where the fluid is loaded into a load portion of the bore to a second position where the predetermined volume of fluid is ejected out of the bore.
In accordance with another embodiment of the metering device, the metering device includes a delivery passage including an elastic portion. The metering chamber is located in the elastic portion of the delivery passage. The elastic portion of the delivery passage is compressed to eject a predetermined volume of liquid.
In accordance with another aspect of the invention, the inhaler preferably includes an aerosol generator wherein a flow passage has an inlet and an outlet and a pressurized source of fluid, a heater is arranged relative to the flow passage for heating at least a portion of the flow passage; and a metering chamber is in fluid communication with the pressurized source of fluid and is configured to deliver a predetermined volume to the flow passage.
In accordance with another aspect of the invention, a method of dispensing a predetermined volume of medicated fluid in an inhaler is provided wherein the inhaler includes a metering device having a pressurized source of fluid which is in fluid communication with a metering chamber. According to the method, the metering chamber is filled with fluid from the pressurized source and a predetermined volume of the fluid is ejected from the metering chamber into a heated flow passage.